DH family, not sure where to post for advice

My husbands parents borrowed about 9,000$ from him when he was 25, he is now 30. They keep saying they will pay him back but have not. They say they have other bills and can't. Yet they have a new car, go out to dinner, shop, ect. He's asked them for just a monthly payment of 1-200$, but nothing. It kills me and I want to say something to them so bad. He has been against me saying anything since it happened right before we started dating, but now I think he's to the point he doesn't care anymore. Any ideas on how to approach them or what to say? We just had a baby and we could use the extra monthly money coming in.